The strike is due to begin on Tuesday evening
London Underground (LU) says it has made a "very fair offer" in Friday's talks with unions over pay.
RMT members plan to walk out for 48 hours from 1859 BST on Tuesday, causing problems for millions of travellers.
LU offered a four-year deal of 1.5% this year and then the inflation rate plus 0.5%; or a two-year deal of 1% now and inflation plus 0.5% in year two.
The RMT, which wants 5%, says talks will resume on Monday. Before then both sides will consider their positions.
LU has urged the RMT to call off its planned strike action.
A spokesman from business organisation London First said: "London Underground and the RMT must take these positive talks to resolution and avoid a strike.
"Business needs the assurance that in uncertain times London's economy will not take a further body blow."
Another of the unions at the talks, Unite, described the offers as "poverty pay" and said they would support industrial action if the offer was not improved further.